1. Field of the Invention
The invention relates to X-ray tables and more particularly to tiltable tables preferably of the so-clled "90--90" type.
2. Description of the Prior Art
In so-called 90--90 type X-ray tables the table body is pivotally connected to a base or pedestal part so that it can be tilted 90.degree. in either direction from its normal position in which the patient-supporting surface is horizontal. This tilting permits a patient to be examined, in any angular table body position between two vertical positions. X-ray tables of this type are well known. Such a table typically includes a movable tower assembly which supports an X-ray tube within the body. The tower also supports radiation responsive devices, such as, a spot filmer, an image tube, and cameras for viewing the image tube output. These devices are supported above the patient supporting top of the table.
The tower assembly includes a column or tower with a forwardly extending portion that extends into the body of the table and underneath the top. This tower extension is mounted on a carriage for movement horizontally in a direction transverse to the length of the table. The carriage is in turn supported on suitable ways in the body of the table for movement lengthwise of the table proper. The tower projects from the rear of the table body and supports a column or tower upon which a further carriage is supported for movement towards and from the table proper. The further carriage carries the radiation detection device which is also movable throughout substantially the entire length of the table.
The movement of a tower assembly should be smooth and relatively effortless. It also should be linear to maintain accurate and consistent spatial relationship among a patient, the table's X-ray tube and the supported imaging devices. If the movement of the tower assembly and the table top is to be consistent and linear the table must be rigid and accurately manufactured.
Conventionally, tables have been constructed in which an upper frame and connected or integrally formed track elements supported the tower assembly. Such a frame was rigidified by a relatively stiff table top. Body sides and ends of such a table, if provided at all, were little more than a sheet metal shroud which improved the table appearance and afforded some X-ray shielding.
With the advent of movable table tops which are powered, and which have become quite popular, the described conventional table construction became obsolete. Table strength now must be provided by the table body which must be strong enough not only to make up for the stiffening formerly supplied by a table top but also to support the top and the motor and drive assembly which carry and move it.
The problem of table body construction is made even more difficult because the weight of imaging devices which must be supported by the tower assembly, and counterweighted in the table body to accomodate the heavier imaging weights, has steadily increased over the years. Since the interior of the table body must be sufficiently open to permit unrestricted tower assembly and counterweight movement the needed strength must be provided in the body walls.
Prior to the present invention various table constructions have been employed, but none are entirely satisfactory. For example, weldments have been used but these have tended to warp due to stress developed during welding operations and to buckle when placed under load.